MADD Matt

Another pump question. BF xr6t - flash tuned and flowed injectors only (stock pump). After sitting for a couple of hours when starting you need to hold the key on for a few seconds before starting. Strait starting results in pre-ignition or backfire (which blows the PCV hose off). 1: Is this likley to be caused by fuel pressure dissipating when shut down? 2: If yes, are there a few likely causes. I can buy a guage and test but if there are other ways to diagnose the prob with my eyes, or if there is a common fault peeps know about I can save the money. Thanks in advance